The present invention relates to a fuel pump unit of a motorcycle.
In a motorcycle, a mixture air is supplied to an engine by using a carburetor or, in an improvement, a fuel is injected into an intake passage of a throttle body connecting an air cleaner to an engine by using an injector. In the case of the fuel injection system, it is necessary to arrange a fuel pump for pressurizing the fuel, for example, in a fuel tank (refer to Japanese Patent Laid-Open Publication No. HEI 5-99089), or the pump is mounted, for example, to a body frame outside the fuel tank (refer to Japanese Patent Laid-Open Publication No. SHO 57-191173).
By the way, in the case where a discharge pressure of a fuel pump increases to a predetermined value or more, normally, a pressure regulator provided on the most downstream side of a fuel flow passage is opened to restore the excessive fuel into the fuel tank.
However, in the case of providing the fuel pump in the fuel tank, a wide place for installing the fuel pump is necessary in the tank, especially at the bottom surface of the tank, and a shape or a layout of the fuel tank is limited.
Furthermore, a high sealing performance is required between the bottom surface of the fuel tank and the installation surface of the fuel pump. However, the fuel tank is generally made of a steel sheet, and therefore, it is difficult to realize a high sealing performance.
Moreover, when the fuel pump is provided in the fuel tank, the capacity of the tank is reduced.
On the other hand, in the case of arranging the fuel pump outside the fuel tank, although the fuel pump is attached to a part of the body frame, it is necessary to use a high pressure hose for connecting the fuel pump and the throttle body, and therefore, it is undesired to widen the distance between the fuel pump and the throttle body.
That is, when the high pressure hose becomes longer, it becomes difficult to keep the air tightness, it becomes necessary to wind a protector or the like around the outer surface of the hose, and the layout becomes complex so as not to interfere with other parts, providing many problems.
In a case where the fuel pump can be arranged near the throttle body, the high pressure hose becomes shorter, but there are many cases where other equipments are attached to the body frame near the throttle body. Therefore, in some cases, it is difficult to mount the fuel pump .
Furthermore, when the fuel pump is attached to the body frame near the throttle body, it is necessary to simultaneously remove the fuel pump when removing the engine or the throttle body (since the high pressure hose is short), which results in a bad maintenance performance.
On the other hand, in a pump for feeding fuel, when the fuel pump is positioned above the fuel outlet of the fuel tank, it is necessary for the fuel pump to simultaneously suck the fuel, and the load on the pump is increased as the difference in location levels becomes larger. As a result, there is a possibility that the fuel cannot stably be supplied, and there is also a possibility that the pump becomes large-sized for the stable supply of the fuel.
Moreover, when the pressure regulator is provided on the most downstream side of the fuel flow passage, the piping becomes long and complex, thus being inconvenient.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a fuel pump unit of a motorcycle capable of making short a high pressure hose and providing a high maintenance performance.
This and other objects can be achieved according to the present invention by providing a fuel pump unit of a motorcycle in which an engine is arranged at a lower portion of substantially a center portion of a motorcycle body between a front wheel and a rear wheel and a fuel tank is arranged above the engine, wherein the engine is formed, at a rear portion thereof, with an intake port to which an air-fuel mixture supply means is connected and a fuel pump for supplying fuel in the fuel tank to the air-fuel mixture supply means is attached integrally to the air-fuel mixture supply means.
In a preferred embodiment, the engine has a plurality of cylinders to which the intake ports are formed, respectively, and the air-fuel mixture supply means is connected to the intake port formed to each cylinder. A plurality of air-fuel mixture supply means are integrally connected by a connection plate and the fuel pump is mounted integrally to the air-fuel mixture supply means through a stay extending from the connection plate.
The air-fuel mixture supply means has a fuel injection type structure. The air-fuel mixture means is disposed between a lower portion of the fuel tank and the upper portion of the engine and comprises a throttle body provided with a fuel injector. The fuel pump is provided with a pressure regulator to regulate a pressure of the fuel and then to supply a fuel to the air-fuel mixture supply means.
The engine has a plurality of cylinders to which the intake ports are formed and the fuel pump is arranged so that a longitudinal axis thereof is arranged substantially in parallel with a row of the plurality of cylinders. The engine may have a plurality of cylinders to which the intake ports are formed and the fuel pump is arranged so that a longitudinal axis thereof is arranged substantially in parallel with an axis of the plurality of cylinders, the fuel pump being arranged so that a fuel inlet thereof is positioned to a lowermost position. Furthermore, the engine may have a plurality of cylinders to which intake ports are formed and the fuel pump is arranged so that a longitudinal axis thereof is arranged substantially at right angles with a row of the plurality of cylinders, the fuel pump being arranged so as to be inclined backward downward so that a fuel inlet thereof is positioned to a lowermost position.
According to the fuel pump unit of a motorcycle of the present invention of the characters mentioned above, in the motorcycle, the engine is arranged at the lower portion of the center of the motorcycle body between the front wheel and the rear wheel and the fuel tank is arranged above the engine. The air-fuel mixture supply means is connected to the intake port formed at the rear portion of the engine. In addition, the fuel pump for supplying the fuel is attached integrally to the mixture supply means. Therefore, the shape and layout of the fuel tank are not specifically limited, and the inner volume of the fuel tank can be kept properly, and it is also not necessary to consider the sealing performance between the fuel tank and the fuel pump. Furthermore, the high pressure hose for connecting the mixture supply means and the fuel pump can be made short. Moreover, the mixture supply means and the fuel pump can be unitized, and the performance of maintenance can be improved.
Still furthermore, the engine has a plurality of cylinders, and the mixture supply means is connected to each of the intake ports formed to each cylinder. The mixture supply means are integrally connected by a connection plate, and the fuel pump is attached integrally to the mixture supply means through the stay integrally extending from the connection plate. Therefore, the mixture supply means and the fuel pump are unitized, and the performance of maintenance can be improved thereby to increase the degree of freedom in the installation position and direction of the fuel pump.
Furthermore, the fuel mixture supply means is a fuel injection type, which is constituted so that a pressure regulator is provided in the fuel pump and the fuel is supplied to the mixture supply means after regulating the pressure of fuel in advance. Therefore, a long complex piping is unnecessary, and the amount of the fuel injection is also made stable.
Still furthermore, since the fuel pump is arranged so that a longitudinal axis thereof is almost in parallel with a row of the plurality of cylinders, the space behind and under the fuel pump can be expanded.
Still furthermore, the fuel pump is arranged so that a longitudinal axis thereof is almost in parallel with an axis of the plurality of cylinders and the fuel pump is arranged so that a fuel inlet thereof is arranged at the lowermost position. Therefore, the space behind the fuel pump can be expanded, and a stable fuel supply can be realized.
Still furthermore, the fuel pump is arranged so that a longitudinal axis thereof is arranged at right angles with a row of the plurality of cylinders and the fuel pump is arranged to the lower backward position so that the fuel inlet thereof is arranged at the lowermost position. Therefore, the space under the fuel pump can be also expanded and a stable fuel supply can be also realized. The vapor lock of the fuel can be prevented, and further, the fuel hose connecting the fuel tank and the fuel pump can be shortened.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.